Liquid developer composition

ABSTRACT

A LIQUID DEVELOPER FOR ELECTROPHOTOGRAPHY TO BE USED FOR DEVELOPING AN ELECTROSTATIC LTENT IMAGE COMPRISING A FINELY DIVIDED GELTAIN TONER AND A FINELY DIVIDED MATERIAL OF A SUBSTITUTED A-CHLORO-B-(P-METHODY-PHENYOXY)-BCARBOXY-ACROLEIN CONTAINED IN A CARRIER LIQUID HAVING A SPECIFIC DIELECTRIC CONSTANT OF LESS THAN ABOUT 3.5.

United States Patent Ofice 3,812,037 Patented May 21,, 1974 3,812,037 LIQUID DEVELOPER COMPOSITION Yasuo Tamai, Seiichi Taguchi, Kiyoshi Yamada, and Nobuo Yamamoto, Asaka, Japan, assignors to Xerox Corporation, Stamford, Conn. N Drawing. Filed Jan. 21, 1972, Ser. No. 219,903 Int. Cl. G03g 9/00 US. Cl. 252-621 4 Claims ABSTRACT OF THE DISCLOSURE A liquid developer for electrophotography to be used for developing an electrostatic latent image comprising a finely divided gelatin toner and a finely divided material of a substituted a-chloro-B-(p-methoxy-phenoxy)18- carboxy-acrolein contained in a carrier liquid having a specific dielectric constant of less than about 3.5.

BACKGROUND OF THE INVENTION This invention relates to a method for the preparation of a liquid developer for electrophotography and more specifically for the preparation of liquid developers for use in color xerography.

The most widely used methods for obtaining good quality multi-oolored image prints employ the combination of silver halide emulsions and the color development process. The Tanning development process uses a silver halide emulsion system and the so-called dye transfer process (or dye inhibition process) uses the gelatin image obtained by the Tanning development process.

Previously, a color printing process has been invented which is based on the dye transfer process but in which the preparation of the gelatin relief was simplified. Accordingly, a color printing process consisting of the following steps has been developed:

(1) An electrostatic latent image is formed on an in sulating layer made of electrophotographic recording ma terial or electrostatic recording material.

(2) The electrostatic latent image is transformed into a material image by using a fine powder (for instance, gelatin) which can easily absorb an aqueous solution of water-soluble dyes.

(3) The material image thus obtained is fixed by any suitable fixing method.

(4) The material image is made to contact the aqueous solution of a water-soluble dye so that the material image can absorb the dye.

(5) A separately prepared dye-absorbent material having a surface which can also easily absorb the said solution is placed upon the material image so that the dyeabsorbent layer can contact the material image. At this time, the dye is transferred to the dye-absorbent layer and the final image is obtained on the dye-absorbent material.

Upon comparing the Tanning process and dye transfer process, it has been found that the former has a wider scope of application which makes it quite suitable for bulk handling. On the other hand, the Tanning process is insufficient as to fastness to light and preservability of the image when compared to the dye transfer process. The dye transfer process in many respects is similar to printing, and when a large number of copies are to be obtained from the same original, this process tends to be more economical. However, when it is desirable to obtain a small number of copies, the same process proved to be expensive. The reason given for the variation in cost for the same process is that the preparation of the gelatin relief which serves as a sort of plate consumes excessive time and skill.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide an improved process for producing liquid developers devoid of the above deficiencies.

It is another object of this invention to provide a novel process for producing a liquid developer containing gelatin.

Still a further object of this invention is the production of a liquid developer comprising a finely divided gelatin and a finely divided substituted acrolein.

These and other objects of the present invention are accomplished, generally speaking, by forming an imaging material which is employed as a liquid developer comprising a finely divided gelatin and a finely divided organic compound represented by the general formula below by adding an dispersing the said ingredients into a carrier liquid of high electrical insulation havng a specfic dielectrc constant of less than about 3.5:

OOOH

wherein R represents either a hydrogen atom or an alkoxy radical; and R represents either a hydrogen atom, an alkoxyl or a carboxyl radical.

image will be so hardened that it will become insoluble to both cold and hot water. Even after such operation, however, the hardened gelatin image will still retain the function of absorbing or releasing a water soluble dye.

More specifically, the liquid developer of the present invention comprises an organic compound which is represented by the general formula (1) and finely divided gelatin. In the liquid developer which contains the fine grains of the organic compound and those of gelatin, these two compounds are preferably separately dispersed in the carrier liquid because both are charged positively and electrostatically repel each other. Both of the fine grains are attracted by an electrostatic latent .image and adhere to it simultaneously. Fixation may be accomplished by heating after the particles which adhere to the latent image or alternatively heated following steam fixation.

The compound represented by formula (1) reacts with the finely divided grains of gelatin and hardens them. It is desirable that the heating temperature be between the range of to C. If the temperature is below 75 C., it takes a longer time to harden the fine grains of gelatin, while if the temperature is about 140 C., the color occlusion ability of gelatin deteriorates. The heating-up time varies inversely in proportion to the temperature. For instance, at a temperature of 80 C., a heatingup time of about 40 seconds is required while at a temperature of 90 C., the hardening of gelatin is completed in about 10 seconds.

With the use of the liquid developer obtained by the present invention, the gelatin relief can be manufactured according to the following steps:

(1)) An electrostatic latent image is formed on the insulating layer of an electrophotographic recording material or electrostatic recording material.

(2) The electrostatic latent image is developed by any suitable method using the liquid developer of the present invention.

(3) The material image thus obtained is fixed by an appropriate method such as, the use of steam.

(4) The recording material on which the fixed image resides is heated-up thereby hardening the gelatin.

The gelatin relief thus obtained is used to contact the aqueous solution of a water soluble dye thereby causing the gelatin relief to absorb the dye. Then a separately prepared absorbent material having a surface which easily absorbs the said dye solution is placed upon the said gelatin relief so that the dye-absorbent layer can contact the gelatin relief. At this time, the dye is transferred to the dye-absorbent layer and the final image is obtained on the dye-absorbent material.

It is desirable that the organic compound be watersoluble and/or methanol-soluble and it is necessary that the said compound be insoluble in the carrier liquid. Because of these properties, it is desirable that R of general formula (1) be either a hydrogen atom, a methoxyl or an ethoxyl radical and R be a hydrogen atom, a methoxyl or a carboxyl radical. The organic compound is crushed into fine grains by the Wet or dry crushing method and used as the imaging material.

Fine grains of the compound represented by formula 1) can be the conventional spray drying process either employing a solvent or non-solvent for the compound. The finely divided particles of the said compound thus obtained is dispersed into the carrier to be employed as an electrophotographic developer.

It is feasible to impregnate the fine grains of gelatin with the organic compound beforehand, but this practice has proven to be undesirable for long-term preservation. During the period of preservation, the organic compound hardens the finely divided gelatin even though very slowly so that fixation by steam of the developed image thus obtained becomes difiicult. This defect naturally becomes negligible when the long-term preservation of the organic compound is not required or steam is not used in fixation.

The finely divided gelatin contained in the liquid developer can be obtained by any suitable technique, e.g. the conventional dry crushing process or wet crushing process which may be employed. The sedimentation process consisting of the addition of an aqueous solution of gelatin into a non-solvent for gelatin, or the spray drying process in which an aqueous solution of gelatin is sprayed into dried air may also be employed. Other methods have been developed wherein alcohol is added to the aqueous solution of gelatin so long as the agglomeration of gelatin does not occur. A gelatin dispersoid substance is made by adding a water-alcohol mixture solution of gelatin to a solvent compatible with water which is a non-solvent for gelatin; then only the finely divided particles of gelatin are collected from this dispersoid by the flocculation process, thereby replacing the dispersoid solvent with the carrier liquid.

Any suitable carrier liquid may be used in the present invention. Particularly desirable are carrier liquids having an electric resistance of about 5 x ohm./cm. and having a dielectric constant below about 3.5.

Any suitable amount of gelatin may be added to the carrier liquid. Desirable results have been obtained by adding 0.005 to 5 parts by weight of gelatin to 100 parts by weight of the carrier liquid. If the quantity of gelatin 4 in the carrier liquid is very small, it is impossible to de velop fully the electrostatic latent image on the photosensitive layer, whereas if the concentration of the gelatin is too high, fog is liable to occur.

Any suitable amount of the organic hardening compound dispersed in a carrier liquid may be used. Satisfactory results have been obtained when the organic compound is used in the range of about 0.0001 to about 0.05 parts by weight per 1 part by weight of gelatin. If the concentration of the organic compound is very low, gelatin hardening by the post-treatment will be insufficient. Whereas, if the concentration of the organic compound is very high, the quantity of the fine grains of gelatin which will adhere to the electrostatic latent image will become insufficient, thereby deteriorating the optical density of the image obtained by dye transfer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following preferred examples further define, describe and compare preferred materials, methods and techniques of the present invention. In the examples all parts and percentages are by weight unless otherwise specified.

EXAMPLE I Five grams of photographic gelatin is added to grams of distilled water. After 30 minutes, the gelatin becomes swollen. By heating this gelatin at a temperature of 65 C., a transparent aqueous solution of gelatin is obtained.

While 10 ml. of this aqueous solution of gelatin is maintained at a temperature of 45 C., 11 ml. of methanol is added to it until the solution becomes slightly cloudy. The addition of 0.5 ml. of distilled water makes the solution clear again. Thus, a water-methanol mixed solvent solution of gelatin is obtained. The total quantity of the mixed solvent solution is dispersed in the following manner by the supersonic wave dispersion method;

M. Acetone 980 Cottonseed oil 20 Varnish obtained by heating the rosin modified phenol formaldehyde resin and linseed oil grams Toluene The resin component in the varnish is insoluble in acetone, but soluble in the carrier liquid.

Immediately upon the addition, resin gelatin agglomerates were observed to be formed in the solution. After 30 minutes almost all of the agglomerates had settled, the supernatant liquid is removed by decantation. 800 mls. of acetone are added to the precipitate and stirred. After being left for 15 minutes, the supernatant liquid is removed and 200 mls. of liquid containing the precipitate is obtained. After treating the liquid by a centrifugal separator, a resin precipitate containing finely divided grains of gelatin is obtained. The total quantity of this precipitate is added to the following mixed solvents and stirred:

Ml. Toluene 20 Xylene 3.5 Cottonseed oil 6 master liquid is poured into the carrier having the following composition:

Thus, a light milky-white liquid developer for electrophotography is obtained.

Kerosene is added in order to order the evaporation velocity of the liquid developer. The gelatin in the liquid developer has a positive charge.

0.1 gram of oc-chloro-fi-carboxy-B-phenoxy-acrolein is wet-crushed together with 5 ml. of cottonseed oil and 25 ml. of kerosene in a small-sized ball mill, thereby giving a suspension. The total quantity of this suspension is added to the liquid developer containing gelatin as above described and thoroughly stirred. The dispersion stability of the developer thus obtained is found to be satisfactory when employed as an electrophotographic developer.

EXAMPLE II 100 parts of photoconductive zinc oxide and 20 parts of epoxy ester of dehydrated caster oil fatty acid are mixed with an adequate quantity of toluene to provide a homogeneous liquid. To this liquid, 0.02 part of fluorescein and 0.2 part of tetra-bromophenol blue are added after being dissolved in a small quantity of ethylene glycol monomethyl ether, and thereby the photosensitivity of the zinc oxide is expanded to the entire visible region of the spectrum. After an adequate quantity of toluene is added, this liquid is applied to an aluminum-evaporated polyethylene terephthalate film (thickness 90 1.). After the application of liquid, the thickness of the film is about 8 1.. When the film is thoroughly dried in a dark place, it acts satisfactorily as a photosensitive material for electrophotography. This electrophotographic material is exposed to a negative corona discharge in a dark place so that its surface can be charged uniformly. Then, a color slide transparency which is used as an original, is fitted into an enlarger and a red filter is fitted to cover the slide. The negatively charged photosensitive material is exposed by the projection of the color slide by the enlarger.

The exposed photosensitive material is wetted with kerosene and quickly immersed in the liquid developer as provided in Example I. At this time, a developer tray made of stainless steel is used. By bringing the latent image surface near the bottom of the tray, the latter is made to act as a developing electrode. The developed sheet is removed from the tray after immersion for about 90 seconds, and then it is washed with isoparafiin (Isopar E manufactured by Esso Standard Oil Co.) and dried.

After the drying, the developed sheet is exposed to steam so that the gelatin image can be fixed, and then the entire sheet is heated up in an air thermostatic oven which is maintained at a temperature of 100 C. The heating up period is 10 seconds. By his treatment, the gelatin image is hardened and firmly adhered to the surface of the photosensitive layer. This imaged member may then be employed in an imaging process as before described.

EXAMPLE III A solution having the following composition is prepared in order to remove the zinc oxide from a conventional photosensitive layer:

M1. Glacial acetic acid 40 Distilled water 60 6 the sheet is thoroughly washed in distilled water. Finally, the sheet is immersed in methanol, taken out and dried by the blowing of warm air.

Using the above-mentioned procedure, a gelatin relief suitable for cyan printing is obtained employing the tech nique as before described.

EXAMPLE IV The procedure as outlined in Example III is again performed except that a green filter is employed and a gelatin relief for the magenta print is obtained by the same development treatment.

EXAMPLE V The procedure as described in Example III is again performed except that a gelatin relief for a yellow print is obtained by the combination of the same original and a blue filter.

EXAMPLE VI The three gelatin reliefs as produced in Examples III, IV, and V are respectively immersed in an aqueous solution of Acid Blue 54, Acid Violet 7, and Acid Yellow 23, taken out and Washed with a wash bath containing acetic acid. A sheet of dye-absorbent material having a gelatin layer is immersed in an aluminum sulfate solution. After being mordanted, the gelatin layer of the dye-absorbent sheet is consecutively pressed into place upon each of the three gelatin reliefs. By this step, the dyes which are absorbed into the respective images are transferred to the gelatin layer. Thus, a reproduction of very high quality is obtained. These gelatin reliefs are found to be satisfactory for reimaging 100 times.

EXAMPLE VII The liquid developer as described in Example I is again employed except that a-chloro-fi-carboxy-B-phenoxyacrolein is replaced by a-chloro-B-carboxy-B-(p-carboxyphenoxy)-acrolein. Comparable results as those of Example I are obtained.

EXAMPLE VIII The procedure as outlined in Example I is again performed except that a-chloro-B-carboxy-fl-phenoxy-acrolein is replaced by lit-chlorop-(p-methoxy-phenoxy)-B- carboxy-acrolein. Comparable results as those of Example I are obtained.

EXAMPLE IX The procedure as outlined in Example II is again performed except that the heating-up conditions after fixation are altered to C. for 20 seconds in order to obtain results comparable to those obtained in Example II.

Although specific materials and operational techniques are set forth in the above embodiments using the developing materials and techniques of this invention, these are merely intended as illustrations of the present invention. There are materials and techniques other than those listed above which may be substituted to obtain similar results.

Other modifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure which modifications are intended to be included in the scope of this invention.

What is claimed is:

1. An electrophotographic liquid developer comprising a finely divided gelatin material and a finely divided hardening compound represented by the general formula:

COOH

wherein R represents either a hydrogen atom or an alkoxyl radical; and -R' represents either a hydrogen atom, an alkoxyl or a carboxyl radical dispersed in a carrier liquid having a specific dielectric constant of less than about 3.5.

7 8 2. An electrophotographic developer according to claim wherein R represents either a hydrogen atom or an alkoxyl 1 wherein said gelatin comprises about .005 to about 5 radical; and R represents either a hydrogen atom, an parts by weight to 100 parts by weight of said carrier lk l b l dic L liquid.

3. An electrophotographic developer according to claim 5 References Cited 1 wherein said hardening compound comprises about 0.001 to about 0.05 parts by weight to 1 part by weight UNITED STATES PATENTS of Sand gelatm- 3,038,804 6/1962 Knox 96-111 4. A process of forming an electrophotographic developer composition comprising adding to an aqueous 10 NORMAN G, TORCI-IIN, Primary Exami r solution of gelatin a finely divided hardening compound 7 represented by the general formula: J. L. GOODROW, Assistant Examiner v R us. c1. X.R. ii; 5 OH 96-111 CH1- =C--C1 15 e110 

